The Complete Guide to Baseballs

Learn how the anatomy of your baseball can impact its performance on the field.

It might just seem like a normal baseball, but the details encapsulated in those 108 stitches mean a lot to the athletes throwing, catching and hitting it. From the interior makeup to the exterior casing, each piece of the ball serves a purpose.

With its signature white surface and figure-eight stitching, today’s modern baseball is as recognizable as the game itself. Learn how the anatomy of a baseball plays an important role in its performance on the field.


When buying baseballs, you can expect to find two exterior materials: leather and synthetic. These materials make up the outer shell of the baseball, called the cover. Long-lasting leather covers are the traditional choice for many baseball players due to their secure grip, consistent play and proven durability.

Synthetic covers, often made of vinyl, can resist dirt and maintain color while remaining a more cost-effective alternative to a than full-hide leather baseballs. Some players purchase synthetic cover baseballs for practice and save the leather baseballs for in-game use.


When it comes to the 108 stitches that are synonymous with the baseball’s profile, there are a few options available to players. The stitching on a baseball typically falls into three categories: raised, rolled or flat.

Raised-seam baseballs have the stitching elevated from the surface of the ball. These seams are designed to “grip” the air for easier control and are used for casual play or instruction. Beginner baseball players can also benefit from using raised-seam baseballs.

Rolled seams have far less elevated stitching, giving them less air resistance than raised seams, while remaining comfortable to grip. Many competition-level baseballs (including Little League, high school and professional baseballs) use this style of stitching.

As the name suggests, flat-seam baseballs lie flat against the surface of the ball, which can make them more difficult to grip and control. Flat seams are great for use in pitching machines, however, as the minimal stitching creates less interference for a clearer trajectory.


It’s what’s on the inside that counts. Just below the cover is where your baseball gains its bounce and worth, thanks to the connection between a baseball’s core and windings.

At the heart of your ball lies a small, round center called the core. The core consists of cork, rubber or a combination of the two. Cores can differ in density to better suit the league they are designed for, which are typically stamped on the cover.

Wrapped around the core you will find thick layers of wool yarn or a wool blend. The wool windings have a high compression threshold and can help extend the life of a baseball.

In addition to your baseball’s lifespan, the wool windings can also affect your ball’s circumference. Baseballs recommended for competitive play are between 9 and 9 ¼ inches in circumference.


For younger players, especially those just learning the game, safety should remain a prime concern with any equipment piece. To help soften the structure of a baseball, and aid youngsters in overcoming their fear of being hit, manufacturers offer specialized “Reduced Injury Factor” balls. These balls have a softer, typically polyurethane core, and come in both reduced and official weights. They perform like regular balls, bouncing and rolling true to expectations.

Understanding the ins and outs of baseball construction can help you take the field with confidence this season. Catch these Pro Tips and choose the right baseball for you.